Field
Exemplary embodiments relate to a vehicle motor control system and method, and more particularly, to a vehicle motor control system and method that may change the number of turns in a coil of a motor according to the speed of the motor.
Discussion of the Background
An electric vehicle (EV), which is an example of an “eco-friendly vehicle” (Eco-Car), obtains a driving force through a vehicle motor that uses a vehicle battery as a power source. Due to the increase in weight and cost of the vehicle battery, a vehicle motor is designed and controlled such that it may be driven within a limited voltage range.
Due to an electric current limit, a vehicle motor needs high counter electromotive force to generate a maximum torque during low-speed running. To this end, a design for increasing the number of turns in a series coil of the motor is needed. Here, the counter electromotive force is expressed as the product of a magnetic flux linkage of a coil of a vehicle motor and a rotational speed of a rotor of the vehicle motor.
Since a counter electromotive force is proportional to a rotational speed of a rotor of a vehicle motor, a counter electromotive force of a vehicle motor designed to be efficient in a low-speed running range may exceed a vehicle battery voltage during a high-speed running range.
Therefore, in order to achieve optimization for high-speed running, the counter electromotive force should be generated to be less than the vehicle battery voltage limit. Thus, a design for decreasing the number of turns in a series coil of a motor is needed. However, when the number of turns of the motor is decreased and also when high torque is needed, high electric current should be input. Accordingly, a copper loss (P=I2r) that is expressed by a winding resistance r and the square of a winding current I and a winding resistance r may increase, and efficiency may decrease.
Generally, once determined, a design for the number of turns of a coil of a vehicle motor cannot be changed while the vehicle motor is running. Thus, there are many difficulties involved in designing the number of turns of a vehicle motor such that performance required during low-speed running and performance required during high-speed running may be satisfied at the same time.
The above information disclosed in this Background section is only for enhancement of the understanding of the background of the invention and therefore it may contain information that does not constitute prior art.